[ClojureScript] Re: Using `not` for keywords
There is no protocol for "truthiness", which is what you want. nil and false
are false, everything else is true.
Even if there were a protocol for truthiness, you could not use :yes and :no
(keywords), you would have to create your own custom type and implement the
protocol on it. (Think about it: what if the truthiness of a *specific* keyword
depended on application code you didn't write? E.g. if some library globally
redefined the truthiness protocol on keywords so that :no is false?)
Clojure is philosophically opposed to making truthiness user-definable. Many
other languages (including lisp and scheme) have not-very-simple truthiness
rules that Clojure deliberately simplified. Allowing user-definable truthiness
would bring all that complexity back *and then some*.
You have a problem-domain-specific use of :yes and :no and a
problem-domain-specific notion of truthiness. You can either use functions
which implement that domain notion (which you have done, and which is the best
approach I think), or you can write your *own* protocol for this and extend it
either to custom YES NO types or keywords.
You could also create a boundary in your application where you convert from a
:yes-:no representation to a more native true-false.
It smells like a bad design that you have the *same* function and code
accepting both :yes and :no *and* true and false. Since this is a
domain-specific problem and type, it seems like the same code shouldn't be used
in both cases. I.e., your "not" function should be:
(defn a-not [answer]
(case answer
:yes :no
:no :yes
(throw (ex-info (str "Not a valid questionnaire answer: " (pr-str answer))
{}
On Wednesday, January 14, 2015 at 2:50:21 PM UTC-6, Yehonathan Sharvit wrote:
> In my app, I am using :yes and :no sometimes instead of true and false.
>
>
>
>
> I’d like to know what is the best way to extends the `not` function to be
> able to handle :yes and :no properly.
>
>
>
>
> I was expecting some kind of Boolean protocol but I wasn’t able to find it.
>
>
>
>
> I could write this:
>
>
>
>
>
>
> (defn not [x]
>
> (case x
>
> :yes :no
>
> :no :yes
>
> (cljs.core.not x)))
>
>
>
>
> (map not [false true :yes :no]); (true false :no :yes)
>
>
>
>
> But I’m not sure it is the most idiomatic solution.
>
> Any ideas?
>
>
>
> —
> Sent from Mailbox
--
Note that posts from new members are moderated - please be patient with your
first post.
---
You received this message because you are subscribed to the Google Groups
"ClojureScript" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojurescript+unsubscr...@googlegroups.com.
To post to this group, send email to clojurescript@googlegroups.com.
Visit this group at http://groups.google.com/group/clojurescript.
[ClojureScript] Re: Using `not` for keywords
Boolean is not a protocol. It is a native datatype, just like in Clojure. -- Note that posts from new members are moderated - please be patient with your first post. --- You received this message because you are subscribed to the Google Groups "ClojureScript" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojurescript+unsubscr...@googlegroups.com. To post to this group, send email to clojurescript@googlegroups.com. Visit this group at http://groups.google.com/group/clojurescript.
[ClojureScript] Re: Using `not` for keywords
On Thursday, 15 January 2015 19:19:37 UTC+2, Thomas Heller wrote: > On Thursday, January 15, 2015 at 5:08:27 PM UTC+1, Yehonathan Sharvit wrote: > > Because in my app , it is clearer from a semantic point of view, it is > > clearer as the value stands for a question asked to the user. > > How about > > (ns my-ns.util) > > (def YES true) > (def NO false) > > (ns my-ns >(:use my-ns.util)) > > (map not [false true YES NO]) > > > Using :yes/:no will really eat into your ability to use anything that expects > true/false. > > HTH Maybe my app is not well designed. But I'd expect clojurescript to allow me to implement the boolean protocol for any type, in the same way I can extend the Seqable protocol -- Note that posts from new members are moderated - please be patient with your first post. --- You received this message because you are subscribed to the Google Groups "ClojureScript" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojurescript+unsubscr...@googlegroups.com. To post to this group, send email to clojurescript@googlegroups.com. Visit this group at http://groups.google.com/group/clojurescript.
[ClojureScript] Re: Using `not` for keywords
On Thursday, January 15, 2015 at 5:08:27 PM UTC+1, Yehonathan Sharvit wrote: > Because in my app , it is clearer from a semantic point of view, it is > clearer as the value stands for a question asked to the user. How about (ns my-ns.util) (def YES true) (def NO false) (ns my-ns (:use my-ns.util)) (map not [false true YES NO]) Using :yes/:no will really eat into your ability to use anything that expects true/false. HTH -- Note that posts from new members are moderated - please be patient with your first post. --- You received this message because you are subscribed to the Google Groups "ClojureScript" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojurescript+unsubscr...@googlegroups.com. To post to this group, send email to clojurescript@googlegroups.com. Visit this group at http://groups.google.com/group/clojurescript.
[ClojureScript] Re: Using `not` for keywords
Because in my app , it is clearer from a semantic point of view, it is clearer as the value stands for a question asked to the user. -- Note that posts from new members are moderated - please be patient with your first post. --- You received this message because you are subscribed to the Google Groups "ClojureScript" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojurescript+unsubscr...@googlegroups.com. To post to this group, send email to clojurescript@googlegroups.com. Visit this group at http://groups.google.com/group/clojurescript.
[ClojureScript] Re: Using `not` for keywords
On Wednesday, January 14, 2015 at 3:50:21 PM UTC-5, Yehonathan Sharvit wrote: > In my app, I am using :yes and :no sometimes instead of true and false. > > > > > I’d like to know what is the best way to extends the `not` function to be > able to handle :yes and :no properly. > > > > > I was expecting some kind of Boolean protocol but I wasn’t able to find it. > > > > > I could write this: > > > > > > > (defn not [x] > > (case x > > :yes :no > > :no :yes > > (cljs.core.not x))) > > > > > (map not [false true :yes :no]); (true false :no :yes) > > > > > But I’m not sure it is the most idiomatic solution. > > Any ideas? > > > > — > Sent from Mailbox If you are passing around :yes and :no as values in your code and want to treat them like boolean values, why not pass around true or false instead? -- Note that posts from new members are moderated - please be patient with your first post. --- You received this message because you are subscribed to the Google Groups "ClojureScript" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojurescript+unsubscr...@googlegroups.com. To post to this group, send email to clojurescript@googlegroups.com. Visit this group at http://groups.google.com/group/clojurescript.
